1. Field of the Invention
The present invention relates to a printed circuit board, an IC card or CSP (chip scale package) using the printed circuit board, and a method for manufacturing the printed circuit board.
2. Related Art
In manufacturing a printed circuit board, as shown in FIG. 24(a), at first, an adhesive 8 is applied onto one surface of the substrate 1 and, as shown in FIG. 24(b), the substrate 1 is die-cut to thereby form an opening 3a for loading a part therein as well as a plurality of openings 4 for insertion of bonding wires therethrough. After then, as shown in FIG. 24(c), a metal foil 9 such as a copper foil or the like is adhered to one surface of the substrate 1 with the adhesive B. Next, the metal foil 9 is worked by etching or the like for circuit configurations, with the result that, as shown in FIG. 24(d), there are formed contact terminals 2 which provide outer contacts with the surfaces thereof exposed to the outside. By the way, the bottom surface of the part loading opening 3a as well as the respective bottom surfaces of the plurality of bonding wire openings 4 are formed of these contact terminals 2, while each of the contact terminals 2 formed on the bottom surface of the part loading opening 3a also has a function to hold the electronic part 5. After the circuit is configured in this manner, as shown in FIG. 24(e), the portions of the circuit corresponding to the outer surfaces of the contact terminals 2 as well as the portions thereof facing the bottom surfaces of the openings 3a and 4 are respectively plated with Ni and Au to thereby produce two kinds of finishing plating 10a and 10b.
However, each of the contact terminals 2, as described above, is formed of the metal foil 9 adhered to the substrate 1 with the adhesive 8 and, therefore, the contact terminal 2 can peel off when the adhesive 8 is caused to deteriorate due to the action of high temperatures; that is, the contact terminal 2 raises a problem relating to the heat resistance thereof. Also, the thickness of the printed circuit board is increased by an amount corresponding to the adhesive 8, which makes it difficult to reduce the thickness of the printed circuit board.
Further, because the openings 3a and 4 are formed by die-cutting, there is a limit to reduction in the diameters of the openings 3a and 4 and it is also difficult to reduce the distance between the openings 3a and 4. That is, there is a limit to reduction in the size of the printed circuit board.
Also, when forming the two kinds of finishing plating 10a and 10b respectively on the portion corresponding to the outer surfaces of the contact terminals 2 and the portion facing the bottom surfaces of the openings 3a and 4, such plating operations are executed in the same process. Actually, however, it is difficult to execute such different kinds of plating in the same processs that is, the portion corresponding to the outer surfaces of the contact terminals 2 must be plated with Ni and glossy Au to thereby produce the fishing plating 10a, whereas the portion facing the bottom surfaces of the openings 3a and 4 must be plated with Ni and non-glossy Au to thereby produce the fishing plating 10b.
On the other hand, the circuit board manufacturing process for CSP is described in Unexamined Japanese Patent Publication Hei 4-3676.
However, this technique has a problem such that when forming an opening (which corresponds to the term "opening" disclosed in the present application) extending up to the surface of a circuit pattern such as a connecting terminal, there is used a carbon dioxide laser. However, due to use of the carbon dioxide laser, the resin forming the substrate cannot be removed completely. Also, when a plated conductor is formed on the circuit pattern surface, or when the plated conductor is connected to the circuit pattern surface by soldering or by wire bonding, such connection provides a low connecting reliability.